Copper-aluminum-manganese alloy



Patented July 20, 1943 UNITED STATES PATENT OFFICE corrsn-awmmm-mncansss ALLQY Cresap Moss, Salt Lake City, Utah, assignorto Chicago Development Company, Chicago, Ill.

No Drawing. Application August 15, 1941,

. Serial No. 407,004

to about 3% manganese, approximately 7.5%

aluminum, balance copper, the tensile strength is decreased and the elongation increased over such alloys which are devoid of manganese. With an increase of manganese in such alloys above 4%,

the tensile strength increases and the elongation- These properties result when conven-' decreases. tionalcommercial silico-thermic or aluminolthermic manganese is utilized in the preparation of the alloys.

' In accordance with the present invention, when alloys of the aforementioned type are made irom high purity manganese which is essentially free from iron and from the oxides of aluminum and silicon, which impurities are present in commercial silico-thermic and alumino-thermic manganese, entirely different results are obtained and m the resulting alloys have new and highly, im-

proved properties. In order to bring about these results, manganese of a purity of at least 99% should be employed and, for best results, it is especially desirable to utilize electrolytic manganese having a purity of about 99.9%.

In an illustrative example of an alloy made in I accordance with the present invention, an alloy was prepared by melting together aluminum, manganese and copper to produce an alloy containing 8% aluminum, 1% manganese, and the balance copper. The metals utilized were all highly pure, the aluminum being Hoopes process aluminum, and the manganese and copper being of the electrolytic variety and having a purity of at least 99.9%. The alloy was cast in a chill mold and hot rolled at 1600 degrees C. The incorporation oi. the 1% of manganese in the alloy increased the elongation from to 50%, in two inches and, at the same time, the tensile strength was increased-from 32,000 pounds per square inchv to 48,000 pounds per square inch. Increasing the manganese to 2% of the alloy, while maintaining the aluminum content at about 8%, resulted in decreasing the elongation only slightly, namely, to 46% in two inches, while the tensile strength was increased to 60,000 pounds per square inch.

on sand cast alloys containing about 7.5% aluminum, as much as 6% of high purity manganese may be added without decreasing the 60 v elongation from its original value of and the tensile strength of such alloys is increased from approximately 20,000 pounds per square inch to 40,000 pounds per square inch. The ability thus greatly to improve both the tensile strength and elongation characteristics of these alloys is of material value;

As indicated hereinabove, the aluminum content of the alloys of the present invention, in its broadest aspects, ranges from about 7% to about 9% and the manganese content ranges ,Imm abou'. 1% to about 10%. A particularly preferred range is represented by those alloys which contain-from about 7.5% to ,about 8% of aluminum and from about 1% to about 6% or, better still, from about 1% to 2.5% manganese.

While the best results of the present invention appear to be obtained by utilizing electrolytic manganesev or at least 99.9% purity, other forms of substantially pure manganese may also be.

used such as vacuum distilled manganese and the like. The iron content at the finished alloys should not exceed 0.05% andoxides 01' aluminum and'silicon should be essentially entirely absent.

' Those skilled in the art will readily understand the various uses to which the alloys of the present invention'may be put in the light of the characthe oxides of aluminum and silicon and containing not more than 0.05% iron.

2. An alloy containing approximately 7.5%-

aluminum, from about 1% to about 6% man- .ganese having a purity oi at least 99%, balance substantially all copper, the alloy being essentially entirely free from the oxides of aluminum and silicon and containing not more than 0.05% iron, said alloy having an elongation in the sand cast condition or at least 30% in two inches and having a tensile strength greater than 20,000 pounds per square inch.

3. An alloy containing approximately 8% elecs I trolytic aluminum, from about 1% to 2.5% electrolytic manganese having a purity otat least 99.9%, balance substantially all electrolytic cop- Per, said alloy being essentially entirely free from the oxides of aluminum and silicon and containns less than 0.05% mm, the alloy having, in

* the-hot rolled condition, an elongation greater CRESAPEMOSSM 

